Process Control Monitoring (PCM) structures are semiconductor monitoring structures that can be used prior to singulating a semiconductor wafer into individual die. Monitoring with PCM structures can help determine whether fabrication processes are within appropriate process windows or whether individual devices that make up an Integrated Circuit (IC) are within device specifications.
Existing PCM systems, however, present cost and performance disadvantages by placing PCM structures and their conductive contact pads in the same region. For example, in block PCM designs, a region of the wafer that would otherwise be used to form a semiconductor chip is used to form one or more PCM structures and contact pads thereby reducing the number of chips per wafer. For wafers with only a few large semiconductor chips, these block PCM designs sacrifice a large fraction of the productive part of the wafer. Thus, when large semiconductor chips are used, PCM structures and their contact pads are often placed within the lanes where the dies are singulated. Yet singulating through metal pads can introduce imperfections that reduce production yield and create reliability problems for the semiconductor chips that are produced. For example, when mechanical sawing is used to singulate the die, vibrations introduced through the combination of metallic and non-metallic materials that differ in hardness can cause cracks, cavities, or other forms of surface and/or sidewall damage. Furthermore, because metallic and non-metallic materials exhibit different thermal behavior, singulating with a laser introduces material stresses due to dissimilar heating.